I think I’ve settled on the latter. Disagreement is maybe best communicated by the absence of an upvote? And downvotes work best when they signal something that is just off base, and while not reportable, is not appreciated at a broad cultural level.
I’ve always been partial to “irrelevant to the discussion”.
For example: if a post is detailing increased temperatures compared to a previous year: ✅ Comment saying “This is most likely an effect of global warming” ✅ Comment saying “This paper is potentially biased as the paper/publication is sponsored” ✅ Replies to these comments discussing the legitimacy of their claims (for or against them) ⛔ Comment which is promoting their own content (even if related) with no discussion of the linked post ⛔ Intentionally incendiary comments. “Liberals will say it’s climate change I bet.” ⛔ Completely off topic. “Ok but guys let’s talk about SCARING THE HOES for a second here. Straight flames.”
Too many people use a downvote as “I disagree” when a comment may actually provide a different viewpoint and - as long as it’s respectful and open to counterpoints itself - can be a nice addition to the discussion.